All over the world, there is a great demand for implants and grafts. The number of available allografts, that is, human donor organs, is limited, however. Moreover, the allotransplantation causes rejection reactions of the implants, which may be reduced only by immunosuppression or denaturation of the tissue by cryoconservation. This frequently leads to side effects of immunosuppression or a loss of the substitute tissue or organs caused by a rejection. Thus, allotransplantation leads to an increased life span or an improvement in the quality of life, but native tissue cannot be replaced by a conventional allotransplant without risk or the full quality of life restored to the patient.
Because of this, the past years have seen an intensive search for alternative sources of tissue for grafts and implants.
In order to increase the number of available grafts, research has been performed in the field of xenotransplantation using material from animals, especially pigs. But xenotransplantation is open to new hazards, such as the transference of animal diseases to humans.
A further possibility for overcoming the aforementioned problems is the production of bioartificial tissue, also referred to as tissue engineering. In the production of bioartificial tissues, presently biological matrix substances based upon collagen or biodegradable plastics are used as matrices. Thereafter, these tissues are populated with primary human cells that were obtained from human biopsies and subsequently expanded in vitro.
Matrices on the basis of biodegradable plastics, however, exhibit the disadvantage that the conversion of the plastic matrix into functional connective tissue-matrix protein-structures or the re-synthesis thereof is not possible in a sufficient degree given the cell culture conditions used. Therefore, the biochemical composition and the geometric structure of matrices comprised of biodegradable plastics, representing important distinguishing factors for the cell growth, are unsatisfactory.
For this reason, in recent years a lot of research work has focused on the usage of biological matrices.